To make it clear: The trademark is the combination of the sign (e.g. the word or logo) and the goods and services it is registered for. If you use the same sign for different goods and services then there is no infringement and no watering down/dilution, thus nothing to defend against.
There is a difference when treating well-known trademarks (say Coca-Cola, Sony, Google), however I doubt Waffle House gets over the threshold set for that for being too local (I counted at least 20 states that do not have one) and not sufficiently known by all demographics (if you want to know more read up on the Lanham Act).
Full disclosure: I am a TM lawyer, but not in the US. YMMV and what I write here is no legal advice ;-) since only gathered from US colleagues' explanations regarding cases clients had in the US.
The notorious/well-know concept is part of an international treaty (Art. 6bis of the Paris Convention) and its interpretation is similar in most western countries, so I'd expect the US interpretation to not be that far off.
Thanks for explaining and lending your expertise.
Though, I am, again not a lawyer, but I am 99% sure you can't go use the Waffle House logo to sell anything, let alone waffles. I only say that because no one is using, say, the Coca-Cola brand to sell shoes, and if they did, we all know Coca-Cola would prevent that. That goes for any trademark in the US. So perhaps trademark law is different here?
Also, Waffle House are ubiquitous as a brand in the United States - certainly not as well known as Coca-Cola or Sony, but I have no doubt they'd be able to prove national awareness in any demographic.
In this particular case if you look at the C&D, it is for the trademark usage. It's likely that this person could have simply removed the trademark from the page and it would have been fine.
edit: I think the key in other industries would be proof of brand dilution - that is, if you start using the Nike logo to sell waffles, Nike would send a C&D if not a team of lawyers because you are diluting the trademark. So I guess you're technically right, although functionally, brand dilution is easily provable.
No prob. Just some random bits I found looking around for clues whether there already were any decisions from US courts wrt whether Waffle House is a well-known trademark:
Interestingly enough, Waffle House is mentioned in a 2007 article related to a US trademark law reform as an edge case [1].
This does not seem to be the first time that Waffle House appears to be overreaching: [2]. The balls to pull this off with a straight face, kudos to the colleagues.
An article from INTA relating to dilution [3].
[1] https://scholarship.shu.edu/cgi/viewcontent.cgi?article=1864... page 458, last paragraph and footnote [2] https://www.techdirt.com/2011/08/17/waffle-house-says-rap-so... [3] https://www.inta.org/fact-sheets/trademark-dilution-intended...
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